V-band clamps, also referred to as marman clamps, are a type of band clamp widely used in industrial and aerospace applications to detachably join or affix adjacent structures to one another. Marman clamps for payload separation systems are described in “MARMAN CLAMP SYSTEM DESIGN GUIDELINES”, NASA Preferred Reliability Practices Guideline No. GDED-2214, (hereinafter, “NASA Guidelines”) the content of which is hereby incorporated by reference into the present application. Referring to FIG. 1, band clamp arrangement 100 may include one or more band clamps (sometimes referred to as “straps”) 110 and tensioning devices 120. A number of V-segments (referred to herein as “shoes”) 130 are arranged on the interior surface of clamp 110. Band clamp arrangement 100 is configured to encircle abutting cylindrical flanges on each of two parts that are affixed to each other. Tensioning device 120 may include a bolt or stud 122, nuts 124, and end fitting 126. Tensioning of band clamp 110 creates an inward radial restraining force on the shoes which in turn wedge together the abutting cylindrical flanges (i.e., 1001 and 1002) of the two parts to be joined in the axial direction. The two parts to be joined may, for example be pipes, interface flanges of structures or vehicles, including aerospace systems such as launch vehicles and launch vehicle payloads.
As noted in the NASA Guidelines, structural failure of marman clamps are known to have occurred and “extreme care” is urged in designing such equipment.
The assignee of the present invention designs and manufactures spacecraft for communications and broadcast services. Structures of such spacecraft commonly include a structural interface ring which mates to a launch vehicle adapter ring by way of a marman band clamp that also serves as a separation system. During ground integration and test activities, the spacecraft is frequently mated to and demated from ground support equipment (GSE), such as handling dollies. A reusable marman band clamp, such as band clamp arrangement 100, may be detachably secured to the spacecraft structural interface ring, and to an abutting cylindrical flange on the GSE. While so mated, the band clamp will often experience high loads. For example, the spacecraft may undergo dynamic environmental testing while mated to a vibration machine; as another example, a spacecraft handling dolly may hold the spacecraft in a horizontal position during various integration activities, during which the reusable band clamp is required to restrain loads resulting from the cantilevered weight of the spacecraft.
During a spacecraft manufacturing life cycle, a considerable number of mating/demating operations may occur, using the reusable band clamp arrangement. As a result, operator error in installing the band clamp arrangement, and fatigue or other wear of the band clamp and/or its tensioning device, increase the risk of a structural failure that could result in a sudden breaking away of the spacecraft from the GSE. Consequences of such a failure may include injury or death of personnel, and structural damage to the spacecraft and nearby equipment.
In light of this risk, more reliable band clamp arrangements are desirable.